Interactive Molecular Dynamics

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Number of atoms = 250
Box size =
Gravity = 0.000
Time step = 0.020
Steps per frame = 25
Atom color:
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t = 0, E = 0, T = 0, P = 0

This web app simulates the dynamics of simple atoms and molecules in a two-dimensional universe. The force between the atoms is weakly attractive at short distances, but strongly repulsive when they touch. Use the simulation to explore phases of matter, emergent behavior, irreversibility, and thermal effects at the nanoscale.

Note: This version of the simulation includes an enhanced Presets menu to accompany the figures and selected exercises in the accompanying article (pdf), published in the American Journal of Physics 83 (3), 210-218 (2015), arXiv:1502.06169 [physics.ed-ph]. Here is a version of the exercises from the article that includes specific directions and hints for use with this software. For a version of this simulation with the original (shorter) Presets menu, click here.

The physics:

The user interface:

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Gathering data:


“If, in some cataclysm, all of scientific knowledge were to be destroyed, and only one sentence passed on to the next generation of creatures, what statement would contain the most information in the fewest words? I believe it is the atomic hypothesis (or the atomic fact, or whatever you wish to call it) that all things are made of atoms—little particles that move around in perpetual motion, attracting each other when they are a little distance apart, but repelling upon being squeezed into one another. In that one sentence, you will see, there is an enormous amount of information about the world, if just a little imagination and thinking are applied.”

Richard Feynman